Molecular biomarkers as predictors of response to neoadjuvant chemoradiation therapy in rectal cancer

Predicting neoadjuvant chemoradiotherapy response with functional imaging and liquid biomarkers in locally advanced rectal cancer

INTRODUCTION

Non-invasive predictive quantitative biomarkers are required to guide treatment individualization in patients with locally advanced rectal cancer (LARC) in order to maximise therapeutic outcomes and minimise treatment toxicity. Magnetic resonance imaging (MRI), positron emission tomography (PET) and blood biomarkers have the potential to predict chemoradiotherapy (CRT) response in LARC.

AREAS COVERED

This review examines the value of functional imaging (MRI and PET) and liquid biomarkers (circulating tumor cells (CTCs) and circulating tumor nucleic acid (ctNA)) in the prediction of CRT response in LARC. Selected imaging and liquid biomarker studies are presented and the current status of the most promising imaging (apparent diffusion co-efficient (ADC), K^trans, SUV_max, metabolic tumor volume (MTV) and total lesion glycolysis (TLG) and liquid biomarkers (circulating tumor cells (CTCs), circulating tumor nucleic acid (ctNA)) is discussed. The potential applications of imaging and liquid biomarkers for treatment stratification and a pathway to clinical translation are presented.

EXPERT OPINION

Functional imaging and liquid biomarkers provide novel ways of predicting CRT response. The clinical and technical validation of the most promising imaging and liquid biopsy biomarkers in multi-centre studies with harmonised acquisition techniques is required. This will enable clinical trials to investigate treatment escalation or de-escalation pathways in rectal cancer.

Non-operative management of rectal cancer: understanding tumor biology

The management of locally-advanced rectal cancer involves a combination of chemotherapy, chemoradiation, and surgical resection to provide excellent local tumor control and overall survival. However, aspects of this multimodality approach are associated with significant morbidity and long-term sequelae. In addition, there is growing evidence that patients with a clinical complete response to chemotherapy and chemoradiation treatments may be safely offered initial non-operative management in a rigorous surveillance program. Weighed against the morbidity and significant sequelae of rectal resection, recognizing how to best optimize non-operative strategies without compromising oncologic outcomes is critical to our understanding and treatment of this disease.

Predictive and prognostic biomarkers for neoadjuvant chemoradiotherapy in locally advanced rectal cancer

Locally advanced rectal cancer is regularly treated with trimodality therapy consisting of neoadjuvant chemoradiation, surgery and adjuvant chemotherapy. There is a need for biomarkers to assess treatment response, and aid in stratification of patient risk to adapt and personalise components of the therapy. Currently, pathological stage and tumour regression grade are used to assess response. Experimental markers include proteins involved in cell proliferation, apoptosis, angiogenesis, the epithelial to mesenchymal transition and microsatellite instability. As yet, no single marker is sufficiently robust to have clinical utility. Microarrays that screen a tumour for multiple promising candidate markers, gene expression and microRNA profiling will likely have higher yield and it is expected that a combination or panel of markers would prove most useful. Moving forward, utilising serial samples of circulating tumour cells or circulating nucleic acids can potentially allow us to demonstrate tumour heterogeneity, document mutational changes and subsequently measure treatment response.

Germ line polymorphisms as predictive markers for pre-surgical radiochemotherapy in locally advanced rectal cancer: a 5-year literature update and critical review

PURPOSE

Locally advanced rectal cancer is currently treated with pre-surgical radiotherapy and chemotherapy. Approximately one-half of patients obtain a relevant shrinkage/disappearance of tumour, with major clinical advantages. The remaining patients, in contrast, show no benefit and possibly need alternative treatment. To provide the best therapeutic option for each individual patient, predictive markers have been widely researched. This review was undertaken to evaluate recent progress made in this field.

METHODS

A systematic literature search was performed using PubMed and Scopus database, focused on germ line gene polymorphisms as biomarkers and response and toxicity as outcomes. Because an exhaustive previous review was available describing findings up to 2008, we restricted our analysis to the last 5 years.

RESULTS

Ten original research articles were found, reporting promising results for some candidate genes in drug metabolism (TYMS, MTHFR), DNA repair (XRCC1, OGG1, CCND1) and inflammation (SOD2, TGFB1)/immunity (IL13) pathways, but with no firm conclusion. All the studies had small sample size and were defined as exploratory. This review highlights pivotal molecular, clinical, genetic and statistical issues in the investigation of genetic polymorphisms as outcome predictors for rectal cancer and offers suggestions for future development.

CONCLUSIONS

What emerges is a clear need for new proposals, especially in view of the increasing evidence for tumour-host and gene-gene interactions during anticancer treatment, together with stronger adherence to proper methodological requirements.

Predictive markers of response to neoadjuvant therapy in rectal cancer

BACKGROUND

Neoadjuvant therapy followed by radical surgery is the standard treatment in locally advanced rectal cancer. It is important to predict the response because the treatment has side effects and is costly. The aim of this study was to establish the relationship among clinical, pathologic, and molecular biomarkers and the response to neoadjuvant therapy.

METHOD

A total of 130 patients with locally advanced mid and low rectal cancer who underwent long-course radiotherapy with 5-FU based chemotherapy followed by radical surgical resection were included in the study. Clinical and pathologic data were collected. Paraffin-embedded sections obtained in diagnostic biopsies were assessed by immunohistochemical staining for molecular markers and classified using a semiquantitative method. Results were related with T-downstaging and tumor regression grade using Mandard scoring system on surgical specimens.

RESULTS

Pathologic complete response was found in 19 patients (14.6%), while in another 18 (13.8%) only minor residual disease was seen in the rectal wall. T-downstaging was observed in 63 (48.5%). The average of lymph node retrieval in the surgical specimens was 9.4. Regarding predictive markers of response, there was significant correlation between the expression of B-cell lymphoma 2 (P = 0.005), β-catenin (P = 0.03), vascular endothelial growth factor (P = 0.048) and apoptotic protease activating factor 1 (P = 0.03), tumor differentiation grade (P < 0.001), and response in the univariate analysis. T-downstaging was associated with vascular endothelial growth factor expression (P = 0.03) and tumor differentiation grade (P < 0.001). Significant parameters found in the multivariate analysis were tumor differentiation grade and Bcl-2 expression.

CONCLUSIONS

Pathologic and molecular biomarkers in the diagnostic biopsies may help us predict tumor response to chemoradiation in rectal cancer patients.